US slaps travels bans on 14 Iranian officials
While the US State Department did not name 13 individuals, US Secretary of State Mike Pompeo referred to them as "assassins" who posed as Iranian diplomats, Reuters report.
He said the group, who are now barred from travelling to the US, had acted under government orders to "silence opposition and show that no one is safe from the Iranian regime".
Pompeo was likely referring to the 1990 killing of Kazem Rajavi, a then leading opposition figure who was shot near his home in Switzerland, according to relatives.
Rajavi's sister, Maryam Rajavi, was the leader of a prominent leftist guerrilla group known as the People’s Mujahideen, which is still considered Iran's largest and most active opposition group.
The organisation's European office in Paris issued a statement at the time saying the Iranian embassy in the Switzerland was behind the killing.
"The United States will continue to pressure Iran to treat its own people with dignity and respect" Pompeo said on Friday.
The State Department named a 14th individual, Hojatullah Khodaei Souri, the director of Iran's notorious Evin Prison, saying the institution he ran was "synonymous with torture and other cruel, inhuman, or degrading treatment or punishment".
Tensions between Washington and Tehran have soared ever since President Donald Trump in 2018 withdrew from an Iran nuclear deal with six major powers, struck by his predecessor Barack Obama, and reimposed crippling sanctions on Iran.
On Thursday, Pompeo announced the US would activate a "snap back" mechanism to restore all UN sanctions on Tehran, including an arms embargo, arguing the country had violated terms of the nuclear deal, despite Washington abandoning it.
Russia and China, along with European allies Britain, France and Germany, came out to declare the US action "illegal".
This was based on the absurdity of withdrawing from a deal, before using the resolution that endorsed it to re-impose sanctions.
Analysts fear the US move could lead to a crisis of credibility for the UN Security Council, the organisation's most powerful body.
Agencies contributed to this report.